Proper tooth brushing, including length and coverage of brushing, helps ensure long-term dental health. Many dental problems are experienced by individuals who either do not regularly brush their teeth or who do so inadequately, especially in a particular area or region of the oral cavity. Among individuals who do brush regularly, improper brushing habits can result in poor coverage of brushing and thus surfaces that are not adequately cleaned during a cleaning session, even when a standard brushing regimen is followed. Electric cleaning devices, such as electric toothbrushes, have been shown to greatly increase the efficacy of a cleaning session.
These electric cleaning devices, including power toothbrushes, shavers, and similar devices, have a motor, such as a mechanical, electromechanical, magnetic motor, that engages a drive train in order to drive a brushhead in an oscillating, reciprocating, or other pattern. The high-speed oscillating movement of the drive train shaft of the device requires special bearings to constrain motion to only rotation about the center axis. However, existing bearings are not perfectly suited for the high-speed oscillating movement of the drive train shaft. For example, although sleeve bearings are simple and cheap, they are problematic due to power loss from friction and from rattling between the shaft and bearing. Ball bearings have low friction, but are not well-suited to oscillating movement due to poor distribution of lubrication and need for axial loading to reduce noise. In addition, ball bearings are complex and expensive. None of the existing bearings utilized in these specialized drive trains achieve the goal of being quiet, low-cost, low-friction, and simple.
Accordingly, there is a continued need for personal care devices with drive trains having bearings that constrain motion to only rotation about the center axis, and are quiet, inexpensive, and low-friction.